I noticed that they all seem to be redirected so that the http://setiboincdata.ssl.berkeley.edu/sah part of the URL is replaced with http://setiweb.ssl.berkeley.edu when the link is used, and then the error message only shows the part not replaced, as follows for the "Windows/x86" link:

Not Found
The requested URL /download/boinc_3.20_windows_intelx86.exe was not found on this server.
--------------------------------------------------------------------------------Apache/1.3.31 Server at setiweb.ssl.berkeley.edu Port 80